Yes, it was never Printed onto more camera negative film, it was printed onto Positive release stock...which is "negative" working in that the tones are reversed from the negative, thus making a positive.

Wait, I'm confused... What is the difference between camera film and release film?

Release film has a clear base, to show whites as brilliantly as possible on screen, while camera film usually has a mask. Also, release film is extremely fine grained and slow (I think Eastman 7302 is around ISO 3) and optimized for the task at hand. Printing onto camera stock is of course possible but yields inferior results.